Infrared Exposure meter conversion

[adrian_wilson6]

Hi,

No excuse now for guessing IR levels, a simple IR exposure meter conversion from

a LUX meter, find all the details on ....

 

 

http://www.999wed.com/pg/pg9-infrared-allenmeter.htm

 

 

Leave it with you.

 

Cheers,

 

 

Adrian.

[carbon_dragon]

I have a minolta digital meter that was converted for Kodak HIE film. It works great, so the conversion is possible. I don't think the guy I bought it from still sells it and it was a lot more expensive (but worth it).

[adrian_wilson6]

Hi David,

 

 

I'm plucking up the courage to dismantle my Mk IVf although I should be more confident about this, but it was nice to see the LUX meter swing into life reading IR.

 

Cheers,

 

Adrian.

[helenbach]

Is there an IR blocking filter to limit the spectral sensitivity of the meter to IR, and match that of the film in use? I have found that that is quite important when metering for IR films: the meter must not be more sensitive to the longer wavelengths than the film is.

 

Best, Helen

[adrian_wilson6]

Hi Helen,

 

 

It's all on the site, you can configure the meter to suit your own purposes, even with interchangeable filters if you wish.

 

 

Cheers,

 

 

Adrian.

[helenbach]

Adrian,<p>

 

Thanks for the reply, but the aspect I mentioned doesn't appear to be covered on your website. It was explained in the replies to your first question <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00Karc">here</a>.<p>

 

It is easy to find the correct IR pass filter (it would be the one you use on the camera) but it is slightly more difficult, and expensive, to find the correct IR blocking (short wave pass) filter and maybe it would be worth adding that to your instructions. The addition of the short wave pass filter dramatically improves the ability of the meter to be used with different sources. It is less important if the meter is used only with sources for which it has been calibrated - but then you might as well use a normal unmodified lightmeter.<p>

 

A Minolta Booster II is also easy to convert, and as they can be bought for USD 25 nowadays (less than GBP 15) an IR converted one would be worth considering as an addition to any of the Sekonic or Minolta meters that can be used with them. They are also very sensitive, and they read out in normal exposure units, thus avoiding the need for conversion tables. Apart from the filter there is no need for additional equipment and it is a very easy conversion. I'd be happy to give information about the conversion I did to either the Minolta Booster II or the Pentax Digital Spotmeter.<p>

 

Best, Helen

[adrian_wilson6]

Hi Helen,

 

As a matter of interest what browser are you using, as a lot of the info is placed in Hyperlink tips on mouse over.

 

Kind Regards,

 

Adrian.

 

I recommend FireFox 2 the fastest solution for surfing the net and better than a speed upgrade. AA

[helenbach]

Hi Adrian,

 

"As a matter of interest what browser are you using,"

 

Firefox 2.

 

Best, Helen

[helenbach]

I should have added that I can see the info when I mouse over, but I didn't see any info about a short wave pass filter. Did I miss something?

 

Thanks,

Helen

[kunihiko]

I've been thinking the same thing as Helen mentioned - Short Wave Pass filter would be requiered depends on the spectral sensitivity of the photo diode used in the meter.<BR>

From what I have read, some photo diodes has its sensitivity peak at around 950nm and lose sensitibity at 1000nm-ish, some have its peak at 800nm and start to lose sensitivity at 900nm-ish. On the second case, you may not have to worry much about SWP filter thing, I guess.<BR>

Has anyone got spectral sensitivity curves of the photo diode used in the meters mentioned above ?<BR>

Since the SWP filtets are bit expensive, photo diode which has spectral sensitivity suited for IR photography without a SWP filter would be nice.<BR>

Which meter would be preferable on this regard ?

[helenbach]

The meter is USD 34 (about GBP 17) including postage, so it is easy enough to get one to test.

 

Though the 50 mm x 50 mm SWP filters are fairly expensive, you don't need much to cover the sensor, if they are required. They can be cut like glass. I normally just give away any surplus pieces I have. Maybe it would be worth putting together a little kit with SWP filters to match SFX200, Maco 820 and HIE. I've suggested a similar thing before and got almost no response. I'm not really interested in doing this commercially, nor do I wish to compete with someone who is doing it commercially, so that suits me fine.

 

Best, Helen

[adrian_wilson6]

Hi,

 

Just a quick update, the site now has minor changes and additions >> for those that missed the link here it is again ...

 

 

http://www.999wed.com/pg/pg9-infrared-allenmeter.htm

 

 

I must make it clear as Ms Bach has inferred that I am undertaking this conversion as a commercial venture, this is not true. Details of the conversion have been placed on the site to assist fellow Photographers and I have had the site verified by a couple of people in the trade over here, all say it is excellent and have no problems whatsoever following the instructions. I have offered to undertake the conversion for people that would not feel happy doing it themselves, however I do not keep units in stock that are converted and neither do I keep components, as I do not envisage undertaking this task as it is so easy to complete but the offer is there.

 

 

On another tack, the Minolta conversion takes another step closer to fruition, including a couple of steps backwards ( That was Funny ). A link is also in place for a Lux to Ev values conversion, works out interesting when you set it out as a graph.

 

Cheers for now,

 

Adrian

[helenbach]

Adrian,

 

I made no inference that you were doing this as a commercial venture, I merely stated that I had no interest in competing with anyone who was.

 

Best,

Helen